Prof Dieter Jaksch

Abstract:

The ability to store multiple optical modes in a quantum memory allows for increased efficiency of quantum communication and computation. Here we compute the multimode capacity of a variety of quantum memory protocols based on light storage in ensembles of atoms. We find that adding a controlled inhomogeneous broadening improves this capacity significantly.

Abstract:

We investigate the dynamics of Rydberg electrons excited from the ground state of ultracold atoms trapped in an optical lattice. We first consider a lattice comprising an array of double-well potentials, where each double well is occupied by two ultracold atoms. We demonstrate the existence of molecular states with equilibrium distances of the order of experimentally attainable interwell spacings and binding energies of the order of 103 GHz. We also consider the situation whereby ground-state atoms trapped in an optical lattice are collectively excited to Rydberg levels, such that the charge-density distributions of neighboring atoms overlap. We compute the hopping rate and interaction matrix elements between highly excited electrons separated by distances comparable to typical lattice spacings. Such systems have tunable interaction parameters and a temperature ∼ 104 times smaller than the Fermi temperature, making them potentially attractive for the study and simulation of strongly correlated electronic systems. © 2008 The American Physical Society.

Abstract:

A technique to measure the decoherence time of optical phonons in a solid is presented. Phonons are excited with a pair of time-delayed 80 fs near infrared pulses via spontaneous transient Raman scattering. The spectral fringe visibility of the resulting Raman pulse pair, as a function of time delay, is used to measure the phonon dephasing time. The method avoids the need to use either narrow band or few femtosecond pulses and is useful for low phonon excitations. The dephasing time of phonons created in bulk diamond is measured to be τ=6.8 ps (Δν=1.56 cm-1). ©2008 The American Physical Society.